Testing system



Feb. 13, 19 23.

s. B, WILLIAMS, JR, ET AL TESTING SYSTEM Filed w b. 5, .1919

fienen A. Boat/er.

l atented Feb. 13, 192

ts sales SAMUEL B. WILLIAMS, an, or BROOKLYN, NEW YORK, AND HERBERTnjnos'ratrna, or WEST NEW YORK, New annsnr, nssrcnons To wnsrnannnno'rrtrc'corirnny, INCORPORATED, on NEW roan, n. 35., A oonrona'rronor NEW YORK.

TESTING SYSTEM.

App1ication fi1cd February which the following is a full, clear,concise,

and exact description.

This invention relates to electrical testing systems, and moreparticularly to testing systems capable of use in connection withtelephone systems employing connecting apiiaratus common to one group ofapparatus, to connect an individual set thereof with an individual setof another group of apparatus. with which the connecting apparatus maybe associated.

A telephone system employing automatic distribution of calls betweencalling subscribers and answering operators through the medium of linefinders and selectors is shown, and one example of such a system isdisclosed in a patent of Samuel B. Williams. Jr., No. 1,304,641, datedMay 27, 191-9. In automatic call distributing systems it is usual toprovide a terminal bank cont .ning multiple sets of a large number orsubscr'ibers lines. Each line has a number of terminal sets individualthereto, located horizontally across the bank and available to a numberor. diiiercnt line finders; the line lindci's being so arranged as toconnect with the terminals of all the subscribers lines in the multiplebank. Each oi the line finders is connected to a particular selector.and a group of these selectors are arranged taining multiple terminalsets of a number oi cords or trunks extending'to diiferent op cratorspositions, a terminal set of each such cordor trunk being availableto'each ot the selectors. Upon a subscriber removing his receiver fromthe hook switch in calling, an idle line finder is actuated to engageone of its brush sets with the terminal set of such line availablethereto, and to extend the connection to the proper brush set of itsassociated selector. The selectorsearches over its terminal bank untilsuch brush set en counters the terminals of an idle cord or to pass overa similar terminal bank con 5, 1919. Serial Macrame.

trunk terminating before an answering op orator, and'stops thereon, thuscompleting the connection of'the calling subscribers l ne to ananswering positlon' The line finder involved and the particular selectorconnected thereto thus serve as connecting apparatus between the callingsubscribers line and the cord or trunk extending to an answeringoperators position.

Each trunk has a signal associated there; with and operated onconnection of a calling line with such trunk to indicate that asubscriber, is calling. Should a line he co n' nccted with a trunk at atime when such line is not in use due to an abnormal condition of line,the trunk signal would be operated in the same manner, although noresponse would be obtained to an operators challenge. The signal isknown under these conditions'as a permanent signal. It is highlydesirable that the line causing the trouble should be readily locatedand removed from service in such away that like difficulties will notrecur pending the restoration of the line to its normal condition. It'isfur ther desirable that such location should be made quickly in orderthat the line finder, the selector, and the trunk involved will not beengaged for an excessive period; thus reducing the available equipmentand impairing the efficiency of the system.

In absence of the present system it would be necessary in such cases tovisit in turn each of the selectors having a multiple of the involvedtrunk until the selector connected to the terminals of such trunk werelocated; From th s selector the particular line finder connectedthereto. would be found, and such line finder visited. The particularset of terminals on which this line finder rests would next be noted.and the numberof the line thus identifiedf Thisline is then removed fromservice, and prevented from eftion is to provide a testing systemcapable of application to telephone systems employ ing a plurality ofsets of connecting appa.

ratus common toa group of sets off appii ratus in which each set ofconnecting zip-- paratus is arranged to connect with any set. of suchgroup, by which any particular set of connecting apparatus connectedwith any set of such group-may be rapidly and accurately located. Inaccordance with this feature of the invention individual test terminalsare provided for each set of connecting apparatus adapted to connectwith the sets of apparatus oi the group, together with means by whichtesting current is supplied to the test terminal of a set of connectingapparatus connected to a set apparatus or the group, and it eanscooperating with the test terminals to determine the particularconnecting apparatus involved in the connection. I

Another object of the invention. is to provide a testing system having atesting circuit associated with a circuit to be tested in which the flowof testing current such that the detection of the testing current isinsured. p

In accordance with this feature of the i11 vention two transformer coilsare provided and arranged tor unsymmetrical connection by threeconducting paths in such a manner that flux produced in the core of thefirst transform-er coil will produce an efi'ective flu in the core ofthe second transformer coil by means oi currents flowing over threecircuits, each includinga different pair of the three conducting pathsand each of the three paths having current flowing thereover so long asall of these three circuits are maintained. The circuit arrangement isalso preferably such that an effective flux will.

also be produced in the core of the second coil whether one two or threeof these cir cuitsbe maintained at the same time.

Other objects and features of the invention, not speciiically mentionedabove, will be ap txarent from the following specification andannexeddrawing illustrating diagrammatically one embodiment of thepresent invention as ai iplied to an automatic call distributingtelephone system.

In the paticular embodiment of theinventiou illustrated, a subscribcfsstation It is sh wn having;- a pair of line conductors 10 and '11,extending); to a central oltice; A. line relaylfi, a cutoff relay 13,and a plurality er calling jacks, such as 14!, individual to the lineare provided. The line relay 12 i 11, an

is ordinarily operated over a circuit extend mg from battery, left-handwinding of relay 2, lett-hand contact ofrelay 13, conductor l thencethrough the right-hand contact f relay 13, and right-hand winding ofrelav 2 to ground. 1 if V In call distributing; systems asapplied tolarge exchanges, it is usual for a calling line to be extended to ananswering opera-- tor, through a line finder associated with a apparatusat substation A, conductor 10,

trated, and the line conductors 10 and llv and the test conductor 15 ofthe subscribers line are inultipled to an individual set or terminals ina multlple terminal bank ava1lable to a number of line finders, any oneof which isdesigned to extend the particular subscribers line to ananswering operator. Two such linev finders, LF and Ll or the usual type,are shown in the present instance. The closure of the contact of relay12 causes the line Ll? to seize the termina s 18 01" the calling linesubstantially asdisclosed in the Williams patent above noted. As furtherdisclosed in the above-noted patent, the cord selector GS is caused toseize an idle cord or trunk extending to an idle operators positionherein shown as the associated circuit connected to the terminal set 21.The operators telephone set is next automatically connected to thetrunl: through the contacts 24: and Qtiot sequence switch, termed forconvenience SS when this switch is moved to position 7 as disclosed inthe patent mentioned. A circuit is also closed from ground, interrupter29, con tact 23 of sequence switch SS conductor 28, contact 26 oranother sequence switch S5,, and lamp 27 to grounded battery. The lamp27 is individual to the trunk concerned, and the flashing signal givenby this lamp serves to identity the trunk over which a call has beenextended to the particular answering}; operator. v

sequence switch SS, having a contact 10 is associated with the finder LFand its associated selector CS, and operates in such a manner as toclose this contact 100 just subsequent to the stopping of the brush set16 upon the terminal set 1.3 of line A. This closure takes place atposition 4 and is maintained until. position 121-, and provides anoperating); circuit for the cutoff relay 13, extending 'trorn grounded.battery, contact 100, sleeve brush of brush set 16 and sleeve terminaloi? terminal set 1.8, conductor 15, and winding oi relay 12-3 to ground.Busy potential is also placed upon the sleeve terminals of the multiplejacks and also upon the sleeve terminals of the multiples of, line A inthe line finder contact banks. The operation of relay 13 opens thecircuit of line relay 12, which releases.

On the engagement of the tip andrin a brushes of the selector C?) withthe tip and ring terminals of set 21.,and' consequent movement of thecontacts 24: and Le oi sequence switch SS, into their seventh posi-vtery, lower'lett-hand winding of repeating marines coil 36 winding ofrelay 69, contart 23 of sequence switch SS in position '7, cnga oil ringterminal and brush of selector cs. engaged ring brush and terminal offinder LF conductor 11. left-hand winding of induction coil. hookswitch, and transi'nitter of station A, conductor 10, engaged tiptcrminal and brush ct finder Ll engaged tip brush and terminal ofselector CS, contact 24 oi sequence switch Si in position 7. and upperleft-hand winding; ot repeating: co l 56 to ground. A circuit is alsopro-videiil through contact 98 of sequence switch or between positions12- and 18 and often, the illun'iination ot the siuaerv-isory lamp {itwhen the supervisory relay (39 is deenergized during such interval, thiscircuit extending from gl'OlllldQd battery. resistance 42 lamp 60. andcontact 98 of sequence switch SS between positions 1%} and 18;} toground. On operation of relay (39, however. over the circuit previouslymentioned, illumination of the lamp is prevented due to a short-cu cuitcompleted about this lamp by the closure of the contact of relay (S9.opening the operating circuit of: relay of) as tor example by restoringthe receiver to the switclrhooiq at stat-ion A. the lamp .60 is.however, illuminated to indicate that disconnection is desired bystation A.

In the present situation the relay (39 being energized prevents theillumination 0t lamp T he operator, under ordinary con ditions nowobtains the number of the called line and completes the connection inthe usual manner. It sometimes occurs, however, that the operatorobtains no response either to her request. for Number please or to hersubsequent challenge Are you calling although the lamp 60 is not.ligz'hted' The failure of the operator to obtain a reply indicates thatsomething is the matter with this line. This condition is known as apermanent signal in stems of this type. This condition may ari. e. {forexample. by the suliscriber leaving his receiver oil the hook. by cond'ons prodi'icingr a short circuit between the line cam-ductors '10 andll. or by grounding tl1erfl funder certain condition... It. is'ohviouslydesirable to determine what line in trouble in order to remove thetrouble and to tree the line finder and selector involved in theconnection so that they can be used in extending other calls.

in the absence of any special testing equipment. in order to locate theline causing the permanent signal, it would be necesto visit in turneach of the cord selecthe particular trunk orcord reported by theoperator is found. From this selector it would be necessary to traceback to the particulsi r line finder connected thereto, and then to notethe position of the terminal set frames until the selector connected toon which the brush set of such line Finder rests, and from this identii. the line involved. flliis line maythen be removed :trom. service theyuse oi? a trouble cord, in the usual manner whichyserves to provide atrouble tcst for all the multiples of such line. To simplify thisprocedure and to save time as well to decrease the liability of error,the present invention contemplates the provision of a testing contactbank 85. Terminals indivii'lual to each of the line finders are arrangedin this bank and connected to the tip and ring; brushes of the brushsets of their respective line finders. A brush set 36 is designed topass over this contact bank and to engage one set of contacts at a time,the number or the line finder whose test terminals are engaged at anytime being denoted by the number on a designation strip 3'? associatedwith the bank indicated by a pointer '38 movable with the brush set 36.flhis bank is for testing purposes and would in practice be locatedconvenient to the switchman. an d a number of trunks would be providedhetween the answering positions oil the main switchboard and theswitchnians desk. The terminal'set individual to line tinder LF isdesignated as 39.

The jack 40 of one such switc'hmanls trunk has been indicated and anoperator having a trunk giving a permanent signal indication may insertthe plug 41 ot such trun lt into the jack 40. This act serves to efi'ectthe movement of sequence switches SS and SS into position 14 and intoringing position, respectively, as disclosed for example, in the patentabove referred to. The lamp 27 is thereuponarranged to burn steadilyover a circuit from grounded battery, lamp 2?, contact 102 of sequenceswitch SS between pov the number oi I sitions 3 to 16 to'ground. .asdisclosed in said patent and remains steadily lighted until theringing'is completed as hereinafter described. The switchman. is now signalledthrough the application 01 alternatinging current to the tip and ringconductors of the plug 41, over a circuit including the source ofringing currentlOB, contact 104 in position 13, the tip contacts ofplus; 41 and ack 40, conductor right-hand winding of relay 44. condenser46, conductor 47. the ring contacts of the jack 40 and plug 41 and thecontact 105 in position 13 to said source 103. The consequent operationof relay 44 illuminates the lamp 48 and provides a direct currentlock'inggcircuit tor relay 44 extending from grounded battery; lamp 48,

contact and left-hand winding of relay 44.

with the jacks 52 and 53 of his trunk, the

switchman, on observing the illumination of lamp 48, inserts these plugsor plugs of a similar switchmans set therein and moves the key 49 tolistening position.

This act automatically disconnects the ringing current, and moves thecontacts of sequence switch S8, into position 17, in which position thelamp 2? is extinguished and the controlling circuit of the callingsupervisory lamp 59 extended to the contact of relay 92. This relay wasactuated upon the insertion of the plug 41 into jack 40 over a. circuitextending from grounded battery, winding oi relay 92, sleeve contacts ofplug 41 and jack 40, and resistance to ground. The contact of relay 92is thus closed during ringing, but completes no circuit until sequenceswitch contact 48 is moved into posi tion 17, upon the switchman movingthe key 49 to listening position. As soon as this is done however acircuit is completed extending from battery, lower right-hand winding ofcoil 56, winding of relay 58, ring contacts of plug 41 and ack 40,conductor 47, upper contacts of key 49, right windings of transtlf'ormercoil 99, lower contacts of key 49, conductor 45, tip contacts of jack 40and plug 41, and upper right winding of coil 56 to the other side ofbattery. Relay 58 is thereby operated thus short-circuiting lamp 59 andpreventing its illumination so long as this circuit is maintained. Theswitchman can signal the answering operator however by opening andclosing the listening key 49, thus alternately opening and closing thecircuit through the relay 58. Its contact is correspondingly opened andclosed, and when opened removes the short circuit about the lamp 59 topermit its illumination over a circuit from grounded battery, resistance97, lamp 59, contact 43 of sequence switch SS, in position 17, andcontact of relay 92 to. ground. The resulting flashing of the lamp 59serves to indicate that the switchman desires to communicate with theoperator, being substantially the same operation of the signals andtheir meaning as in a connection between'a calling and a calledsubscriber.

Although the insertion of the plug 41 into jack 40 effects the movementof the contacts of sequence switch S5, out of their seventh orlistening-in position into their fourteenth or talking position, asdisclosed in beforevmentioned patent, means are available to theoperator as therein described which wlll upon operation efiect themovement of the sequence switch SS again to its llsteningin position andinasmuch as the key 49 is in its listening position'such an act by theoperator will complete telephonic circuits for intercommunicationbetween the operator and the switchman. On obtaining this connection theoperator informs the switchman of the permanent signal on the trunkused.

inthe connection.

The operator would efiect the movement eas es of the contacts ofsequence switch S3, again to its fourteenth or listening-out position,and

the switchman would establish connectionoi? plugs 50 and 51 of aswitchmans set with the acks 62 and of a tone testing circuit,preferably common to all the switchmens trunks, in order to locate theline finder in yolved in the permanent signal connection. The same oranother switchmans set can be used for this purpose, and the circuit ofthe switchmans trunk is such that the disengagement of the plugs 50 and51 from the jacks52 and 53 does not disturb the circuit previouslytraced to maintain the supervisory relay 58 energized to preventillumination of the lamp 59. The transformer coil 99 and jacks 52 and 53may however be common to a number of switchmens trunks, and connected tothe individual trunks by the movement of the key 49 in dividual to aparticular trunk with which connection is desired.

In the present system it is possible for one switchman to answer callsover the switchnians trunk and another switchinan to simultaneouslysearch for line finders in volved in permanent signal connections.

'The switchman answering a call over a switchmans trunk, on beinginformed of the permanent signal connection, and desiring to disconnectfrom such trunk, as for example to answer a call over another trunk,would move holding key 55 into its closed position and also move the key49 of the trunk in use out of listening position. The

operation of key 49 disconnects the coil 99' from the trunk originallyused and leaves it free to be connected to another switchmans trunk bymovement of the key 49 individual to such other trunk. The closure ofkey 55 provides a holding circuit through the relay 58 to prevent-thelamp 59 giving a disconnect signal at this time; this circuit extendingfrom battery, lower Ilglll) winding 0i coil 56, winding of relay 58,ring contacts of plug 41 and jack 40, conductor 47, upper contacts ofkey 55, Winding of retardation coil 5'2, lower contacts of key 55,conductor 45, tip contacts of jack 40 and plug 41, and upper right-handwinding out coil 56 to the other side of battery. Under these conditions none of the lamps 27, 59 and 60 are lighted, and since thiscondition is maintained until after the involved line finder has beenlocated, consequent"annoyance oi the operator by false signals duringthe testing operation is thereby prevented.

Referring to the testing operation, the in sertion oi plug 50 into thejack 62-completes a governing circuit for a tone generator 64, thiscircuit extending from grounded battery, winding of a relay 65,conductor 66, and upper contacts of jack 62 to ground. The energizationof relay 65 completes a'cir-1 cuit to operate the tone generator 64,this ll D i tor of the motor, to conductor (38 and contact of relay 6:")'tothe ground.- switch may be provided to do operating circuit tor thetone generator (it,

it it desired to ope enerator independently ot the The tone generator64; developsalternating current, the frequenc 1: not being preier- Yably such asto produc a tone which can be readily distinguished fromcurrents of other frequencies which may be encountered in testing overthe multiple terminals of line finders engaged at the time; thealtm'uating current thus developed flowing tin primary Winding of atransformer inducing corresponding currents in the secondary Windingthereof.

Each of the switchrnairs truni-is'has a tone he; '72 individual thereto,and in testing over such trunk this key is closed. Undeut conditions theinsertion of the pl J the jack 63 completes a tone cir ut extending fromthe grounded secondary inding of repeating coil 71, conch-rotor 73,resistance 74, lower contacts of jack 63, lett-hand'contacts of tone key72, conductor 41-7, ring contacts oi jack 40 and plug 41, winding ofsupervisory relay 58, and lower right-hand winding of repeating coil 56tln'ouglr irrattery to 'ound. A parallel branch of this circuit extendsfrom the conductor '73, through the righthand contacts of tone key 72,conductor 45, tip contacts of jack l0 and plug l1, and upper right-handvindingot repeating coil 56 to ground. 7 The resistance 74 inserted inthe parallel branch including the ring contacts of the jack 4-0 and plug41 to prevent too great a lieu of direct current over a circuitcompleted upon the insertion. or plug 41 into jack 4:0 and extendingfrom battery, lower right-hand Windingot coil 56, Winding of relay 58,ring co; acts of plug all and jack 40, conductor l7, 3 contacts of key72, lower contacts of 1 G53, resistance 74:, right hand contacts of key2, conductor 45, tip contacts of jack 40 and plug 41, and upperright-hand winding of coiloo to battery. The several windings of thetransformer or repeating coil 56, preterably contain substantially thesame number of turns. on account of its use tor two way telephonictransmission as well as for testing currents, although this particularrelation between the dili'erent windings is not essential to the presentinvention.

A transformer coil 76 has its primary Winding arranged in a circuitconnection bridged across the tip and ring brushes of the brush set 36,and condensers 77 and '78 are positioned in this counection'intermediatethe primary winding and the respective brushes. The primary winding ofthe 7 Exit relay Ga.

coil 76 is non-'symmetrically' "divided lay being "grounded at an"intermediate- P011113 ct its Winding sons to. include a. considerablygreater nuirnber of turns in the tip'side,

51. and jack 6% back to the secondary Winding of the repeating 'coil'76, The trans initter S0 of the switchmans set profs-r ably left out ofcircuit during testing as there is no reason tense it'during the actualtesting. W Y

The switchinan in searchingtor the line finder connected to theinvolveclsubscribers line. moves his brush set 36over the testing bank35 until it encounters the terminal set 39 of: line finder LF havingtesting current thereon, which tact Wlll be ndicated to the switchman bythe production of a charac-v teristic tone in his receiver 79corresponding, in frequency to the frequency of the testing currentsdeveloped by the tone generator 64. I Upon the engagement of the brushset 36, with the terminal set 39, thesecondary windings of the repeatingcoil 56 ill be connected with the dividedprimary= winding of thetransformer coil-76' by three conducting paths lee-tor line finder, testtenninal, brush; and condenser 77 the ring conductor of the trunkselector line finder, test terminal, brush, and condenser 7 8, andground; Three fluctuating current circuits'are accordingly possiblebetween the secondary windings for alternating current, namely, the tipconductor of the-trunk use of the repeating coil 56 and the primarywinding of transformer coil; 76," the first including the uppersecondary Winding of the repeating co il 56, the tip conducting path,upper portion of primary Winding of transformer 7 6, and ground to theother side of such secondary Winding, thesecond circuit including thebattery and other'seo onda-ry Windingof coil 56. the ring conductingpath, the lowei portion of such primary winding, and ground totheot-her' side of such battery, and the third circuit in -cluding bothsecondary windings of coil 56 and intermediate battery in series withthe tip conducting path, entire primary- Windof coil 76 and the ringconducting path.

The unbalancing otthe'primary windings 18 to produce a non-symmetricalcircuit arrangement between the repeating coil 56' and the transformercoil 76, and is such as to insure a resultant flow of fluctuatingcurrent to operate the receiver-79, solong as fluctuating currentscontinue to tlow in any one or more of the three circuits. As a resultof the non-synnnetrica-l arrangement, so long as none of the tlireeconducting paths are open or shortcircuited to fluctuating currents, andfluctuating currents are developed in the secondary windings of the reeatin coil 56 corres ondin current resistance of Which was of low value.

will flow over'each of the three conducting paths, and each of the threementioned circuits Will be maintained. Short circuiting between any twoof the three conducting ,paths will still leave at least one of the.

three circuits operative to produce an effective flow of current 1nv thesecondary Winding of the transformer coil v'76 to operate the receiver79, and it is only ivhen all three of these conducting paths aredirectly short circuitedtogether by a connection of practicallynegligible resistance that all three of these circuits can beeffectively de-- currents flowing over each of these three conductingpaths, so long as tWo or all of the three circuits are effectlvelymaintained. 4 The tip and ring conductors and the ground connection ofthe trunk line are in.-

v olved in the three conducting paths noted, and the tip and ringvconductors of the trunk lineinvolved are, under these conditions,connected through the corresponding brushes and conductors of theselector and line finder involved With the tip and ring terminals towhich the line conductors 10 and 11, respectively, are connected. Shouldthe permanent signal be caused by a grounding of the ring line conductor11, the ring and ground conducting paths mentioned are short circuitedtogether, and While the second and third circuits are thus effectuallydestroyed, the first circuit over the tip and ground conducting paths iseffectively maintained, and flux isdeveloped thereby in. the core of thetransformer 76 by the passage of fluctuating currents through the upperportion of the primary Winding thereof. This flux develops a fluctuatingcurrent in the secondary Winding of the transformer 76, and'thus effectsthe operation of the receiver 79 so that the engagement of the brush set36 upon the terminal set 39 of the line finder itlis desired to locatewill be readily detected. On some types of lines it is possible toobtain a permanent signal paths is effectively maintained and flux isdeveloped thereby in the core of the transformer '76 by the passage offluctuating currents through the lower portion of the primary Winding.This flux similarly effects the operation of the receiver 79 to detecttheengagement of the brush set 36 with the terminal set of the linefinder involved. A permanent signal may also result from a shortcircuiting together of the line conductors l0 and 11, and in such casesthe tip and ring conducting paths are short circuited together. Thistoall intents effcctually destroys the third circuit, but the first andsecond circuits are still effectually maintained, the first over the tipand ground conducting paths, and the second over the ring and poundconducting paths. The passage of the fluctuating currents in the firstcircuit through the upper portion of the primary Winding of transformer76 develops flu}; in the core thereof, Whilethe passage of thefluctuating currents in the second circuit through the lower portion ofthis primary Winding develops flux in the core thereof which is alwaysopposed. to the flu): developed in the upper portion of this primary bythe current in the second circuit. Due however to the unsymmetricalarrangement previously described, these fluxes are unbalanced, and theresultant flux vdevelops a fluctuating current in the secondary windingof the transformer 76, Which in turn operates the receiver 79 inaccordance With the impressed frequency. When the permanent signalarises from a subscriber leaving the receiver of his set removed fromthe hook switch, the situation is for all practical. purposes, the sameas that existing when the line conductors l0 and 11 are short-circuited,and accordingly no special explanation is considered. necessary.

It may however occasionally happen that the condition causing a'iermanent signal will clear itself subsequent to connection to thetesting position, but before the brush set 36 has been engaged with theterminal set of the line finder involved. In this event all of the threecircuits between the secondary windings of the repeating coil 56 and theprimary Windingof the transformer coil 76 are effectually establishedWith the engagement of the brush set 36 With the terminal set of suchline finder.

No short circuit exists between any two or more of the three conductingpaths, and the passage of the fluctuating currents over each of thesecircuits through such portion or portions of the primary Winding oftransformer 76, as are included in the respective circuits, results inthe production of corresponding flux in the core of this trans former.The flux produced by two of these circuits Will lead a directionopposite to that possessed by the flux which the other one or" the threecircuits develops at the same instant, but a preponderance of this:exists in one direction at such instant, and provides resultant fluxeffective to develop fluctuating current in the secondary Winding 01:?the transtormer'io to operate the receiver 79, in accordance with thetrequency of the testing Ctlll'l'l.t, thus indicati the engagement ofthe brush t a. terminals of a line tin it is desired to locate aspreviously descrii'ied. I

The unsymmetrical circuit arrangement described thus insures alternatingsignaling current reaching and operating the receiver irrespective 01"whether the permanent gnal arises from the receiver being off the hookswitch, the short-oircuiting of the conductors it) and 11, or thegrounding of one or the other oi these conductors, and also in eventoithe removal of the condition causing such permanent signal prior to thelocation of the line tinder involved.

The number indicated on the designation strip 37by the pointer 38 atthis time shows the line tinder identified LF on the drawing, to be theone involved. This line finder is at once visited and the number of theterminal set on which its engaged brush set rests noted. From theposition of this terminal set in the contact bank, the number or thelinerepresented thereby may often be directly determined or the number maybe tound by consulting a list or chart of line finder terminals. As soonas the number of this line is determined, the switohman has a plug S tof a trouble cord 85, having its sleeve conductor associated with asuitable source of alternating current inserted into a multiple jack 87of the line A. In practice the tone generator 6-it can serve thissource, in which case another transformer 86 is preferably provided,having its primary Winding arranged in the output circuit with thegenerator 64:, and its secondary winding connected to the sleeve of theplug 8st. 7 On the insertion of the plug 84; into the jack 87, tonecurrent is placed upon all the sleeve multiplesot line A, and produces adistinctive tone in an operators' receiver, upon testing the sleevemultiple of line A. with the tip of a calling plug of a cord or trunkcircuit to determine Whether or not line A is in proper condition toreceive a call. The character of the tone received indicates line A tobe in trouble, and Warns operators against connecting therewith.Obviously, a separate tone generator can be used to supply current tothe trouble cords 85,. if desired. The sleeve terminals of the linefinder. multiples of line A alsohave this current placed on thennbutinasmuch as the cut-oil relay 13 or line 'A is operated upon theinsertion 0]": jack 4: into jack 87, over a circuit extending from atwith grounded battery, secondary Winding of transformer 86, conductor88, resistance 89, sleeve contacts of plug S-Ztand jack 87,0011- ductorl5, and Winding of .relay l3 to ground, to disconnectthe line relay l2and the battery associated therewith from the conductors l0 and 11, lineA, will not :in-

'teri ere with the operation of line finderLF after such line finder isrestored to its normal position; nor with other line finders, inasmuchas the o fieration of relay 13 prevents subsequent actuation ot' relay12 and consequent closure of the starter wire circuit. The restorationof the involved line tinder, selector, and operators and switchmenstrunks to their normal condition may be accomplished in any suitablemanner. One such method is for the switchm an to see that his set isconnected to the jacks 52 and-58 and that the tone key 72 ot' the trunkinvolvcd is open. He next opens the holding key of the switchmans trunkused in the connection, and; alternately closes and opens the key d9 ofthis trunk to flash the operator through the medium of the lamp 59 asearlier described. The operator, in response, effects the connection ofher set with the trunk connected with the selector, as before explained,and the kev 49 is now maintained in listening position. The switchman,then directs the operator to Withdraw the plug ll from the jack 4.0. Theoperator thereupon takes down the connection and the selector 9:, asWell as the operators and switchinen s trunks involved therein, arerestored to normal condition ready for subsequent use as disclosed inthe previouslynoted copending patent application.

9 The above-described method is suitable under ordinary operatingconditions, but in order to further economize the time of the answeringoperators during periods of very heavy trafiic, a number of tone jacks90 may be provided, convenient to the answering operators. Any trunkhaving a permanent no signal thereon would have the plug 41 thereofinserted into a tone jack 90, thereby operating a relay 91, over acircuit extending from grounded battery, winding of relay 92, sleevecontacts of plug 41. and ack 90, conductor 93 and Winding of relay 91 toground. The operation of relay 91 in turn effects the illumination of alamp 94 at the sWitchma-ns position, thereby indicating that atrunkhaving a permanent signal thereon hasbeen 20 plugged into tone jack 90;While the operation of the relay 92 prepares a circuit for the lamp 59,as. previously explained.

This relay 9]. and lamp 94 may, if desired, be common to a large numberof tone jacks 90. Plugging into jack90 completes a tone circuitextending, from the grounded secondary winding of repeating coil 71,conductor 95, resistance 96, ring contacts of jack 90 and plug 41,Winding of supervisory rewinding of relay 58, ring contacts ofplug gizedunder these conditions.

i l and jaclr 90, resistance 96, conductor 95, and secondary Winding oftranstorn'ier '71, to ground. Upon the insertion of plug 4.1 into jack90, ringing current is automatically applied. as previously describedbut due to the completion of the dii ct current circuit just mentioned.1

tne contacts of the sequence switch SS, moved into their position l7,but without lighting the lamp 59, inasmuch the supervisory relay 58v isener- The lamp 27 is extinguished on the movement of contact N2 ofswitch SS, into position 17, leaving the lamps, all extinguished duringsubsequent testing operations.

'lhe switchman observing the illumination of the lamp 9%, would see thatplugs 50 and- 51 of a switchmans set were in the aclzs 62 and 63, aspreviously described, to insure the actuation of the relay 65 andconsequent operation oi? the tone generator 64 and generation of:liuctuating testing currents in the secondary winding of the repeatingcoil 71, as previously described. The switchman then searches over thecontact bank 35 to locate the line finder connected to the line causingthe permanent signal, and on determining this line finder, proceeds tofind the number of: the line represented by the terminal set engaged bythe brush set thereof. He then proceeds to have trouble tone as well.asdirect current placed on the sleeve terminals of this line, in orderthat such line will test in trouble, and in order that the line relayoi. such line will. be operated, as previously described.

The line findermay then be manually re stored to its normal positionwhich effects the restoration of the selector CS to normal and themovement of the contacts of sequence switchSS, to position 1. Adisconnect signal. results from the opening of the operating circuit ol.the relay 69 on disengagement oi? the finder and selector brush. sets 16and 19 from the terminal sets 18 and 21, respectively, and theconsequent illumination of the lamp 60 to indicate disconnection isdesired, as disclosed in the copending Williams patent application. Thelamp 59 is not lighted under t iese circumstances, but the operator onnoting that the plug 41 of the involved trunk is in a trouble jack 90,

disconnects therefrom, extinguishing lamp 9-4 at the switchmansposition,provided no other trunks are engaged in corresponding tone jacks 90 andeiiecting the restoration oi the trunk to normal condition.

The line finder Ll selector CS, and the apparatus used in locating theinvolved line finders are now in their normal condition ready forsubsequent use, and line A is arran "ed to test in trouble, andprevented from a; ,in connecting with any or the line finders until thetrouble has been located and line restored to its normal condition.

From. the above description it will be apparent that it a number ofdifi'erent operators trunlrs having permanent signals thereon areplugged into tone acks 90, the sw tchman can locate all. the linefinders 1n- .voived bv testing over the terminal sets in the bank 35 andnoting all of the line finders lidflllf tone current on their terminalsets in the bank 35. These line finderswould be visited, and theparticular lines involved noted, and removed from service as previouslyexplained. This arrangement is of aid in quickly locating a number oflines having permanent signals thereon, and preventing these lines tyingup line finders and cord selectors, which serve as percentage apparatusfor a number of other lines. It will be further apparent that with thepresent system it is possible to simultaneously search for line findersassociated with trunks connected to switchmens trunks and for linefinders associated with trunks directly en gaged with. tone jacks 90;thus insuring a flexibility of operation desirable in systems of thischaracter.

lVhat is claimed is:

1. An electrical testing system comprising pairs of banks of terminals,selectors permanently connected in pairs and adapted to cooperate withsaid banks respectively, a test terminal for each pair of selectors,means to supply testing current to the test terminal of a pair ofoperated selectors, and means cooperating with said test terminals toindicate the particular pair havingtesting current upon the testterminal thereof.

with said test terminals to indicate the particular set of connectingapparatus involved in such connection.

3. An electrical testing system comprising a group of lines extending toa plurality of diii'ereut positions, a plurality of sets ofautomatically operated connecting apparatus common to said groups, andeach arranged to selectively connect with any line or said group, a testterminal individual to each of said sets, means to supply testingcurrent to a line of said group with which one of said sets is connectedat the position at which such line terminates, and means cooperatingwith said test terminals to indicate the particular one or? said setsinvolved in such connection.

l. An electrical testing system comprisis a group of calling lines, agroup of trunk lines, a plurality of sets or automatic con nectingapparatus common to each oi: said groups and selectively operable toconnect any one of said calling lines to any one of said trunk lines, atest terminal individual to h or said sets, means to supply testingcurrent to the terni'iruil ot' a set connecting a calling line to trunlrline, and means cooperating with said test terminals to indicate theparticular set involved in such connection. l

an electrical testing system comprising a group of calling lines, agroup of? trunk lines, a plurality of sets of automatic con nectingapparatus common to each of said groups and selectively operable toconnect any one of said calling lines to any one oi said trunk lines, atest terminal individual to each of said sets, means to supply testingcurrent to a trunk line with which one oi saidsets is connected, andmeans cooperating with said test terminals to indicate the particularsetinvolved in such connection.

6. An electrical testing system comprising a group of calling lines, aplurality of automatic line finders common to said group and selectivelyoperable to connect any selected one oi said finders to any one ofsaid'calling lines, a plurality of trunk lines, a plurality of selectorscommon to said group of trunk lines associated with said plurality ottinders and each operable to connect with any selected one of said trunklines upon connection otthe finder with which said selector isassociated with a calling line, a test terminal. individual to each oi?said finders, means to supply testing current to a trunk line connectedto a trunk selector, and means cooperating with said test terminals toindicate the particular tinder involved in such connection.

7. An electrical testing system comprising a group of subscribers li es,a group of trunk lines extending to an operators position, a pluralityof sets of connecting appa ratus common to both of said groups and eachselectively operable to connect any line of one group to any line of theother group, a test terminal individual to each ot said sets located ata testing position. connecting means to extend said trunk lines to saidtesting position, means to supply testing current through saidconnecting means to a trunk line extended to said testing position, andmeans cooperating with said test terminals to indiate the particular setconnected to a trunk line extended to said testing position.

8. An electrical testing system comprising a group of subscribers lines,a group of trunk lines extending to an operators position, a pluralityof sets of connecting apparatus common to botho'l' said groups and eachselectively operable to connect any line of one group to any of theother group, a test terminal individual to each of said sets located ata testing position, a plurality of connecting circuits between saidoperators position and said testing position to connect said trunk linesto said testing position, means individual to each of said connectingcircuits to supply testing current to a trunk line connected therewith,and means cooper ating with said test terminals toindicate theparticular set connected to a trunk line connected with a connectingcircuit.

9. An electrical testing system comprising a group of subscribers lines,a group of trunk lines extending to an operators position, a pluralityof setsot connecting apparatus common to both of said groups and eachselectively operable to connectany line of one group to any line of theother group, a test terminal individual to each of said sets located ata testing position, a plurality of connecting circuits between saidoperat'ors position and said testing position to con nect said trunklines to said testingposition, means individual to each of saidconnecting circuits to supply testing current to a trunk lineconnectedtherewith,and means common to said connecting circuitsandcooperating with said test terminals to indicate the particular setsconnected to trunk lines connected with said connecting circuits.

10. An electrical testingsystem comprising a group of subscribers lines,a group of trunk lines extending to an operators position, a pluralityof sets 0t coi'inecting apparatus common to both of said groups and eachselectively operable to connect any line of one group to any line of theother group, a test terminal individual to each of said sets located ata testing position, a source of testing current, means at said'operators position available to said trunk lines through which testingcurrent is applied to a trunk line connected therewith, a signal at saidtesting position associated with said lastnamed means and actuated uponthe connection of a trunk line with such means, and means cooperatingwith said test terminals to indicate the particular set connected to atrunk line connected with the means through which testing current isapplied to a trunk line. Y

11. An electrical testing system comprising a group of subscriberslines, a group of trunk lines extending to different operatorspositions, a plurality of sets of connecting apparatus common to both ofsaid groups and each selectively operable to connect any line of onegroup to any line of the other group, a test terminal individual to eachof said sets located atatesting position, asource of testing current,means at the operators positions and available to said trunk linesthrough which testing current is applied to trunk lines connectedtherewith, a signal at said testing position associated with lastmentioned means and actuated upon C 11UOC- tion of a trunk line withsuch means, and

means common to said means through which testing current is applied andcooperating with said test terminals to indicate the par ticular setsconnected to trunk lines connected with the means through which testingcurrent is applied.

12. An electrical testing system comprising a group of subscriberslines, a group of trunk lines extending to an operators position, aplurality of sets of connecting apparatus common to both of said groupsand each selectively operable to connect any line of one group to anyline of the other roup, a test terminal individual to each or said setslocated at a testing position, a source of testing current, means at theoperators position to which said trunk lines extend and available tosuch trunk lines through which testing current is applied to any of saidtrunk lines connected therewith, a signal at said testing positionassociated with said lastmentioned means and actuated upon connec tionof a trunk line with such means, and testing means common to said meansthrough which testing current is applied and cooperating with said testterminals to indicate the particular sets connected to trunk linesconnected with the means through which testing current is applied.

13. An electrical testing system comprising a group of lines, pluralityof sets of connecting apparatus common to said lines and eachselectively operable to connect with any of said lines, a test terminalindividualto each of said sets located at a testing position, a sourceof testing current, connecting means to extend said lines to saidtesting position, means available to said lines through which testingcurrent is applied to a line connected therewith, a signal at saidtesting position associated with said last named means and actuated uponconnection of a line with such means, means to apply testing currentthrough said connecting means to a line extended to said testingposition, and means common to said connecting means and to said meansavailable to said lines cooperating with said test terminals to indicatethe particular sets connected to lines connected with said connectingmeans and with said means available to said lines.

An electrical testing system compria ing a. group of sets of apparatus,a plurality of sets of other apparatus common to said group and arran edto selectively connect with any set of said group, a test terminalindividual to each'of said plurality of sets, contact means toselectively engage said test terminals, a source of testing current,means to apply testing current to the test terminal of a set connectedwith a set of said group, detecting means associated with said contactmeans to dctc at the engagement thereof with a test terminal havingtesting current applied thereto, and means to directly idei'itify theparticular set upon the test terminal of which testingcurrent isdetected.

151 An electrical testing system comprising a first and a secondtransformer coil each having a core and a winding operatively associatedwith its respective core, three conducting paths to connect threedifferent points of the winding of the first coil to three differentpoints of the winding of the second coil to join said windin s innonsymmetrical electrical arrangement, three circuits each including adifferent pair of said conducting paths and different arrangements ofeach of said windings, and means to develop flux in the core of one ofsaid coils to produce a flow of current in each of the three circuits,said flow of current serving to develop a resultant flux in the core ofthe other coil.

16, An electrical testing system compri ingfirst and a secondtransformer coil, each having a core and a winding operativelyassociated with its respective core, three conducting paths to connectthree different points of the winding of the first coil to threedifferent points of the winding of the second coil to join said windingsin nonsymmetrical electrical arrangement, three circuits eachii'icluding a. different pair of said conducting paths and differentarrangements of each of said. \vindii'igs, and means to develop flu); inthe core oi one of said coils to produce a ("low of current in suchot'the three circuits as are effectively maintained; the flow (itcurrent in such circuits as are effectively maintained serving todevelop an effective flux in the core of the other coil.

17. An electrical testing system comprising a first and secondtransformer coiheach having a core and a winding operatively associatedwith its respective core, three con-' ducting paths to connect threedifferent points of the winding of the first coil to three differentpoints of the winding of the second coil to join in nonsymmetricalelectrical arrangement, three circuits each including a difierent pairof said conducting paths and different arrangements of each of saidwindings and arranged in such a way that at least one of said circuitsis effectively maintained on short circuiting together of any two of thethree conducting paths, and means to develop a flow of current in suchof the three circuits as are effectively maintained on short circuitingtogether of two of the three conducting paths; the flow of currents insuch of the circuits as are effectively maintained serving to develop aneffective flux in the core of the coil.

18. An electrical testing system comprisinga first and a secondtransformer coil, each having a core and a winding operativelyassociated with its respective core, three conducting paths to connectthree different points of the winding of the first coil to threedifferent points of the winding of the second coil to join said windingsin nonsyminetrical electrical arrangement; three circuits each includinga different pair of said conducting paths and different arrangements ofeach of said windings and arranged in such a way that at least one ofsaid circuits is effectively maintained on short circaiting together oftwo of the three conducting paths, and means to develop flux in the coreof one of said coils to develop a flow of current in such of the threecircuits as are effectively maintained on the short circuit ing togetherof two of the three conducting paths; the flow of current in such of thecircuits as are effectively maintained serving to develop an effectiveflux in the core of the other coil.

19. An electrical testing system comprising a first and a secondtransformer coil, each having a core and a winding operativelyassociated with its respective core, three conducting paths to connectthree different points of the winding of the first coil to threedifferent points of the winding of the second coil to join said windingsin nonsymmetrical electrical arrangement, three circuits each includinga different pair of said conducting paths and different arrangements ofach of-said windings and arranged in such a way that two of saidcircuits are each having a. core and av winding opera tively associatedwith its respective core,

three conducting paths to connect three different points of the firstcoil to three different points of the winding of the second coil to oinsaid windings in nonsymmetrical electrical arrangement, three circuitseach including a different pair of said conducting paths and differentarrangements of each of said windings and arranged in such a way thatone of said circuits is effectively maintained on short circuitingtogether of two of three conducting paths, and means to develop flux inthe core of one of said coils to develop a flow of current in thecircuit effectively maintained on the short circuiting together of twoof the three conducting paths; the flow of current in the circuiteffectively maintained serving to develop an effective flux in the coreof the other coil.

In witness whereof, We hereunto subscribe our names this 30th day ofJanuary, A. D.

SAMUEL B. WILLIAMS, JR.

HERBERT L. BOSTATER.

